How to Install a Basement Window in a Concrete Block Wall

basement window
  • 72-96 hours
  • Intermediate
  • 200-300
What You'll Need
Block cutter
Window frame
Drill with masonry drill bit
Tarpaulin (optional)
Support stands

Most modern homes are made out of concrete blocks, which can make fitting a basement window seem very difficult. In actuality, installing basement windows is very easy as long as you have the right tools and materials. It is possible to fit the window and weatherproof the house in a day, although it's best to allow for a whole weekend in case of any problems.

Step 1 - Measure

Measure the window to ensure that you can install it safely in your basement. Measure the size of the window opening and mark it on the wall. Doing so makes it much easier to see exactly where the window will go and how it will work. Contact an architect before disturbing the plant to ensure that you don't damage the house. You will need lintels to provide support for the walls above.

Step 2 - Cut a Hole

Cut a hole in the wall. Make sure that the cut is accurate so that you don't have to waste time filling gaps. Start at the top of the hole and cut slots which can fit the support stands. These stands are optional, but make cutting the hole easy.

Slowly chip the concrete blocks out of the wall. You must also cut any blocks which do not need to be removed completely. The most professional way to do so would be to take the bricks out, cut them, and then turn them around. That means that you won't see any cut edges from the outside of the window; however, most professional builders actually just cut the blocks while they are in place.

Step 3 - Fit the Lintel

Fix the lintel into the wall using cement, making sure that it spans the whole opening and is securely fitted. Allow the lintel to go off before fitting the window.

Step 4 - Fit the Window

Remove the glass from the window and lift the frame into the window. Doing so makes it much easier to lift the window and position it. Carefully position it in the hole and check how it will fit. Add packers at the bottom of the window to level it. Use the included fixing screws to screw the window frame into the opening.

TIP: If you get a basement window that's too large for you to carry comfortably by yourself, get a friend or assistant to help you place it. Glass is expensive and you don't want to take a chance you might break it.

Step 5 - Fill Gaps

Gaps around the window frame need to be filled using filler or cement. Make sure that all of the gaps are filled to improve the energy efficiency of your home.

Replace the glass and clip the plastic supports into position. Doing so securely holds the glass in the right place. If you're using Pilkigton K glass, ensure that it is positioned correctly.